It is not explicitly called the UK sizing, but it is equivalent, for all practical reasons.

Sure, the confusion emerges when UK sizing does not match up with Viberg sizing. I'm consistently a 9.5 UK in most Tricker's lasts and a 10 in Viberg. There is no way I could squeeze into a 9.5 Viberg on the 2030 last, and I may even be TTS to wear anything but the thinnest socks.

Sure, the confusion emerges when UK sizing does not match up with Viberg sizing. I'm consistently a 9.5 UK in most Tricker's lasts and a 10 in Viberg. There is no way I could squeeze into a 9.5 Viberg on the 2030 last, and I may even be TTS to wear anything but the thinnest socks.

The 2030 last, for me, is not that different from that 4497 last in Trickers (I am a 9.5 in both). There might be a slight volume difference. However, the real difference seems to be the thickness and rigidity of the leather that Viberg uses. I have a pair of CXL shoes on the 2030 last, and they feel incredibly comfortable, even a bit loose, but the 9.5 in some of the heavier leathers is pretty stiff and uncomfortable.

I am a 10.5 C on a Brannock device. I found the 9.5 D in Viberg's 151 X CSA to be a touch short, as work boots are supposed to have a half inch or more length in front of the longest toe...the sizing is okay, but is not ideal. I later got some Viberg 251 X CSA in a 10 B that fit me much better. I do not know the last number for these work boots, or even if it's the same last between the two, as the 10 B doesn't feel much narrower at all than the 9.5 D.

The other thing to bear in mind is that the length should fit the heel-to-ball, not the total length of the foot. Although too short on total length is obviously not going to work, too long, within reason, is okay as long as the heel-to-ball length is okay...remember that many styles of footwear have long pointy toes...

Guessing one's size is very hit or miss. Without trying on the different sizes, it can be hard to know which will feel best for you. Of course, some guys have feet that do well in boots anywhere close to the right size, so the fine details don't matter to them...my feet seem to be sensitive such issues.

As an aside, I think it's sleazy to try on boots in a local shop with no intention of buying them there, if you're just trying to get your size right for ordering online. I also think it's sleazy to order boots from a shop with free shipping and free returns, if you're certain you're going to return them and buy them somewhere else. Of course, if you are genuinely thinking of buying from the local shop or the liberal-return-policy online vendor and then change your mind, that perfectly fine. Only you will know what your intentions are.

As an aside, I think it's sleazy to try on boots in a local shop with no intention of buying them there, if you're just trying to get your size right for ordering online. I also think it's sleazy to order boots from a shop with free shipping and free returns, if you're certain you're going to return them and buy them somewhere else.

I am a touch sad that my gmto chukka on the 110 may be having to be put away soon...I just don't think I will be comfy with the thicker socks I have to wear to keep the heel from slipping in the warmer days. I have worn in at least 15 times now and for many hours per wear so I don't think any more breaking in will help it.